In order to collect the overspray coating material included in discharged air discharged from a coating chamber using a filter, this type of coating exhaust treatment system is configured to form a filter covering layer made of a layer of accumulated powder and thereby trap the overspray coating material in the discharged air using the filter covering layer. Accordingly, it is possible to prevent the overspray coating material from directly sticking to the filter, and the filter can be used repeatedly by merely removing the filter covering layer in which the overspray coating material is trapped (or in other words, the coating material-containing powder obtained by trapping the overspray coating material, as the filter covering layer) from the filter through a suitable filter cleaning treatment.
Incidentally, it has been proposed hereinbefore in Patent Document 1 that after being removed from the filter through the filter cleaning treatment, the coating material-containing powder is subjected to a recycling treatment through a heat treatment and a pulverization treatment, and the powder recycled in the recycling treatment is dispersed in the discharged air from the coating chamber once again as powder for forming a filter covering layer, using a powder dispersal means (in particular, see Claims 1 and 2 in Patent Document 1).
It has also been proposed in Patent Document 1 that after being removed from the filter through the filter cleaning treatment, the percentage of coating material in the coating material-containing powder is measured using a measurement apparatus, and based on the measurement result, the amount of the coating material-containing powder and the amount of fresh powder supplied from a storage apparatus, which are mixed in the powder to be dispersed once again by the powder dispersal means, are adjusted (in particular, see paragraphs [0197] to [0199] and FIG. 4 in Patent Document 1).